CONSTITUTION AND TEMPERATURE ON MAGNETIC SUSCEPTIBILITY. 
277 
expected, under the influence of an external magnetic field, to form a perfect junction, 
in other words to become welded together 
Tayloe Jones has obtained an induction as high as 74,200 Maxwells in soft iron 
under strong fields. The tension necessary to pull the surfaces apart in this case will 
7-42 X 10* 
^ ^ 2x 10* dynes/square centimetre, which is about a twenty-fifth 
of the tensile strength of the material. 
(6) On a Magnetic Theoey of Chemical Combination. 
On the theory of chemical action developed by Sir J. J. Thomson, t the determining 
featuie of an atom from the point of view' of chemical combination is the numlier of 
positive valency electrons it possesses. These electrons are dragged from their loose 
attachment to the nucleus, during chemical combination, and pass from one atom to 
another. The two originally neutral atoms thus become oppositely charged and so 
attract one another and form, as it were, an electric doulfiet. Let us look at this 
problem from the magnetic standpoint. Each electron orbit is equivalent to a small 
magnetic doublet and it is interesting to enquire how far the magnetic forces of such 
^ doublets may represent the force of chemical affinity. Recent work on radio-activity, 
the wide deflections of ^-rays, and the diffraction of X-rays, all point to a localisation 
of the electrostatic charges in a minute core or nucleus. Round this nucleus, and 
under its control, the valency electrons (in part responsible for the magnetic properties) 
rotate. It is conceivable, therefore, that the magnetic forces, in addition to the 
important role they play in crystallization, may also in part be responsible for the 
forces of chemical affinity, j 
If, duiing chemical combination, there is a definite transfer of valency electrons from 
one atom to another, we should expect to find an abrupt change in the magnetic 
behaviour of an atom before and after chemical combination. If, on the other hand, 
there is no such electron transference, we might expect that the atoms would preserve 
their magnetic properties, which would be more or less of an additive nature. In a 
remarkable series of investigations, Pascal§ has shown that in a very large number 
of organic compounds, the molecular susceptibility is the sum of the atomic 
susceptibilities of the component atoms, provided the molecule contains no peculiarity 
of molecular configuration—such, for instance, as the ethylene linkage, unsaturated 
atom, or complex nucleus. Thus if xm is the molecular susceptibility, and xa the 
atomic susceptibility of a component atom, we have 
Xm = 2xa + ^. 
where the summation extends to all the atoms in the molecule and A is a positive or 
* ‘Phil. Mag.,’ vol. xli., p. 165, 1896. 
t ‘ The Corpuscular Theory of Matter,’ 1907, Chap. VI. 
t See footnote p. 274. Also W. M. Hicks, ‘Roy. Soc. Proc.,’ A, vol. 90, p. 356. 
§ ‘Ann. de Chim. et de Physique,’ ser. 8, vol. 19, p. 5, 1910. 
